An oxyalkylene polymer obtained by a ring-opening reaction of an initiator and a monoepoxide such as an alkylene oxide is liquid at room temperature and a crosslink-cured product maintains a plasticity even at a relatively low temperature. Accordingly, it has found wide acceptance in a starting material for sealing materials, adhesives and the like. As an example of the oxyalkylene polymer used in sealing materials, adhesives and the like, a moisture-curable compound having a hydrolyzable silicon group in the end as described in (Patent Document 1) and (Patent Document 2) is mentioned.
With respect to the oxyalkylene polymer having the hydrolyzable silicon group in the end, generally, the higher the molecular weight, the more the plasticity of the cured product is increased, but the viscosity of the compound is raised, which notably worsens the workability. When the molecular weight of such a compound is low, the viscosity is decreased, but a cured product is poor in plasticity. For providing the low viscosity while maintaining the plasticity of a cured product, various plasticizers have been so far used.
As the plasticizers, aromatic carboxylic acid esters, aliphatic carboxylic acid esters, glycol esters, phosphoric acid esters, epoxy plasticizers, chlorinated paraffins and the like have been used. However, these plasticizers have a migration property. Accordingly, when they are used as sealing materials and the like, there are drawbacks such as contamination of an area around a sealing portion and an adverse effect on an adhesion.
For solving these problems, a method using, instead of a plasticizer, an oxyalkylene polymer in which one end of a linear molecular chain is blocked with an organic group and a hydrolyzable silicon group is provided in another end (Patent Document 3), a method using a combination of a high-molecular-weight oxyalkylene polymer having a high content of a hydrolyzable silicon group per molecule and a low-molecular-weight oxyalkylene polymer having a low content of a hydrolyzable silicon group per molecule (Patent Document 4), a method using a combination of a high-molecular-weight oxyalkylene polymer having a hydrolyzable silicon group content of 50% or more per terminal group and an oxyalkylene polymer having a hydrolyzable silicon group content of less than 50% per terminal group (Patent Document 5) and the like have been proposed.
These oxyalkylene polymers with the low content of the hydrolyzable silicon group per molecule which are used instead of the plasticizer are synthesized from an oxyalkylene polymer having an active hydrogen group such as a hydroxyl group in the end and resulting from the polymerization in the presence of a catalyst such as an alkali metal catalyst, a metal porphyrin catalyst, a double metal cyanide complex catalyst or a compound catalyst having a p=N bond. Among them, when propylene oxide is used as an alkylene oxide in particular in producing an oxyalkylene polymer with a double metal cyanide complex catalyst, an unsaturated mono-ol is less by produced during polymerization, and a high-molecular-weight monodisperse oxyalkylene polymer which cannot be obtained with an alkali metal catalyst is provided. Thus, it is preferably used.
However, an oxyalkylene polymer with a low content of a hydrolyzable silicon group per molecule which polymer is used instead of a plasticizer has been so far produced by polymerization separately from an oxyalkylene polymer with a high content of a hydrolyzable silicon group per molecule and converting an active hydrogen group such as a hydroxyl group to a hydrolyzable silicon group. Later, it has been used instead of a plasticizer by being added to a relatively high-molecular-weight oxyalkylene polymer with a high content of a hydrolyzable silicon group per molecule. That is, a relatively high-molecular-weight oxyalkylene polymer with a high content of a hydrolyzable silicon group per molecule and an oxyalkylene polymer with a low content of a hydrolyzable silicon group per molecule which is used instead of a plasticizer are produced separately. Thus, a production process has been intricate.
Patent Document 1: JP-A-3-72527
Patent Document 2: JP-A-3-47825
Patent Document 3: JP-A-4-57850
Patent Document 4: JP-A-5-59267
Patent Document 5: JP-A-9-95609